linux-kernel - Re: [PATCH 3/6] exec: Stop open coding mutex_lock_killable of cred_guard

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Message-ID: <202005101331.F0ADFAD@keescook>
Date:   Sun, 10 May 2020 13:33:35 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Rob Landley <rob@...dley.net>,
        Bernd Edlinger <bernd.edlinger@...mail.de>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 3/6] exec: Stop open coding mutex_lock_killable of
 cred_guard_mutex

On Sat, May 09, 2020 at 12:18:06PM -0700, Linus Torvalds wrote:
> On Fri, May 8, 2020 at 11:48 AM Eric W. Biederman <ebiederm@...ssion.com> wrote:
> >
> >
> > Oleg modified the code that did
> > "mutex_lock_interruptible(&current->cred_guard_mutex)" to return
> > -ERESTARTNOINTR instead of -EINTR, so that userspace will never see a
> > failure to grab the mutex.
> >
> > Slightly earlier Liam R. Howlett defined mutex_lock_killable for
> > exactly the same situation but it does it a little more cleanly.
> 
> mutex_lock_interruptible() and mutex_lock_killable() are completely
> different operations, and the difference has absolutely nothing to do
> with  -ERESTARTNOINTR or -EINTR.
>
> [...]
> 
> And Kees, what the heck is that "Reviewed-by" for? Worthless review too.

Yeah, I messed that up; apologies. And I know exactly where my brain
misfired on this one. On a related note, I must stop doing code reviews
on Friday night. :)

-- 
Kees Cook